NFC is a 13.56 MHz carrier based secure communication technology which is used in personal ID, money transaction etc. It is to be noted that NFC communication technology works on the same principle as RF communication technology. Hence, the NFC devices (readers/tags) can interchangeably interact with RF devices (readers/tags). An NFC system includes an NFC tag that contains information and an NFC reader that reads information from the NFC tag. An NFC tag can be an active NFC tag or a passive NFC tag. An active NFC tag generates its own magnetic field to interact with an NFC reader. The passive NFC tag utilizes the magnetic field or radio frequency (RF) field generated by an NFC reader for operation.
When the magnetic field of the NFC reader is incident on the antenna of the passive NFC tag, the tag harvests its power from incident magnetic field. The harvested power is used as a supply to analog modules, digital modules and memory circuits. There are many problems associated with the existing power harvest architectures in passive NFC devices. If power drawn by the passive NFC tag for charging is higher than that could be provided by the NFC reader, the huge inrush current results in overloading of the NFC reader, thus resulting in dV/V violation. Also, the passive tag works without any timing signal which results in inaccurate wakeup sequences. Sometimes, the presence of insufficient field causes false activation of the passive NFC tag and thus results in potential latch-up.